JP2018066879A - Zoom lens for projection and projection type image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens for projection that has a brightness expressed by an F number of about 1.6, can cover a half angle of view of about 30°, and achieves a reduction in size and cost.SOLUTION: First to third lens groups G1 to G3 constituting a zoom lens 40 for projection can be configured as a zoom lens of a type where for example, the first and second lens groups G1 and G2 are moved during zooming, and the first lens group G1 is moved during focusing. Satisfying the conditional expression (1) prevents an excessive reduction in back focus, an excessive increase in back focus while securing a sufficient space on a reduction side, and an excessive increase in lens diameter on the reduction side when a substantially telecentric configuration is adopted on the reduction side.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a projection zoom lens suitable for incorporation into a projector that magnifies and projects an image of an image display element, and a projection image display device incorporating such a projection zoom lens.

  2. Description of the Related Art In recent years, presentations using image display elements such as liquid crystal display elements and reflective display elements or projection display devices using light valves have been widely performed. In the optical system of the projector that enlarges and projects the image of the image display element, long back focus and color unevenness occur due to the arrangement of prisms for combining the light from the three image display elements of red, green, and blue Good telecentric characteristics to prevent the light, and a small F-number (that is, a bright optical system) to efficiently capture light from the illumination system is required. In recent years, in addition to the zoom function, it is often required to have a wide angle of view so that it can be easily installed even in a narrow place.

  As a means to obtain a zoom lens for projection with a long back focus while having such a wide angle of view, a retrofocus type lens structure is often used, and the most magnified lens group has strong negative power. It is common to arrange a lens group having In addition, in the zoom lens for projection, in order to ensure a high resolution and a flat image surface in a wide projection range, the most enlargement side lens group and the most reduction side lens group are fixed at the time of zooming. In many cases, zooming is performed by moving the arranged lens groups, and zooming is performed by moving a plurality of lens groups. Further, in focusing, focusing is often performed by moving the most magnified lens group.

  As described above, in the conventional projection zoom lens, it is necessary to move the lens groups in cooperation in order to move a plurality of lens groups to perform zooming. There is a problem that becomes complicated, and accordingly, the cost is increased.

  However, zooming and focusing in the projector may be performed by zooming in accordance with the screen size, determining the projection size, and then adjusting the focus. In other words, even if the focus is slightly lost during zooming, it is only necessary to adjust the focus again, and it is not necessary to use a zoom lens in which the focus does not shift during general zooming. In this way, a zoom lens with a structure that adjusts the focus shift again during zooming is called a varifocal lens, and, as is often seen in surveillance camera lenses, the zoom position and focus position are set as initial settings during installation. It is used as a zoom lens that only needs to be adjusted once. This type of varifocal lens is a zoom lens that performs zooming and focusing by moving two lens groups. The zoom magnification is changed in one lens group, and the focus is shifted in the other lens group. In general, the focusing is performed again with respect to the focal position.

  By the way, since the optical system for a projector requires the telecentric characteristics on the image display element side as described above, when a varifocal lens is employed, it is difficult to use a two-group configuration, and a fixed group is arranged in front of the image display element. It is possible to do. As a projection zoom lens having such a three-group configuration and using a fixed group on the reduction side, there is one disclosed in Patent Document 1. However, the projection zoom lens disclosed in Patent Document 1 is not satisfactory in terms of brightness and cost reduction because the F number is as dark as 2.5 classes, the number of components is large. Further, there is a configuration such as disclosed in Patent Document 2 in which the number of components is reduced to about 7 or 8 to reduce the cost. However, the projection zoom lens disclosed in Patent Document 2 is slightly dark with an F-number of 2 classes, has a half field angle of up to about 27 °, and the projection distance has to be long, and is improved in terms of widening the field angle. There is room for.

JP 2003-215453 A JP 2010-32567 A

  The present invention has been made in view of the above-described background art, has a brightness of about F-number 1.6, can cover up to a half field angle of about 30 °, and achieves a compact and low-cost projection. An object of the present invention is to provide a zoom lens.

In order to achieve the above object, a projection zoom lens according to the present invention includes, in order from the magnification side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a positive refractive power. The third lens group includes a third lens group, and the distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group change during zooming and focusing. A zoom lens that performs zooming and focusing, and the second lens group is a positive lens that is disposed closest to the magnifying side, has a convex surface facing the magnifying side, and has a convex or concave surface that is weaker or concave than the magnifying side. And a positive lens having a convex surface facing the reduction side, a concave surface on the enlargement side, or a convex lens whose convex side is weaker than the reduction side, and the third lens group is a single lens having a convex surface facing the enlargement side. Consists of a positive lens, and the following conditional expression (1) Satisfactory, the projection zoom lens.
(1) 1.4 <Bf / fw <2.0
However,
fw: focal length of the entire lens system at the wide angle end Bf: air equivalent length of back focus excluding prisms and other flat plates

  The projection zoom lens has a three-group configuration. For example, the first and second lens groups (or the second lens group alone, the second and third lens groups, or the first to third lens groups) are used during zooming. The zoom lens can be configured to move, for example, the first lens group during focusing. In the projection zoom lens, the conditional expression (1) relates to the back focus. That is, conditional expression (1) is for securing a space for smooth cooling by disposing a cross prism, a polarizing plate and other optical members on the reduction side and maintaining an appropriate interval. ing. By exceeding the lower limit of conditional expression (1), it is possible to avoid the back focus from becoming too short, to secure a sufficient space for placing the optical member on the reduction side, and to facilitate cooling and the like. Also, by falling below the upper limit of conditional expression (1), it is possible to avoid an excessively long back focus while securing a space. When a substantially telecentric configuration is adopted on the reduction side, the lens diameter on the reduction side is large. You can avoid becoming too much.

  According to another aspect of the present invention, the first lens unit moves from the enlargement side to the reduction side during zooming from the wide-angle end to a predetermined intermediate focal length position when zooming from the wide-angle end to the telephoto end. At the same time, in zooming from the intermediate focal length position to the telephoto end, the zoom lens moves from the reduction side to the enlargement side. That is, the first lens group draws a movement locus that makes a U-turn in the middle. In this case, although the zooming is performed by only two groups, the shift of the focal position can be reduced, and zooming and focusing become easy.

  According to still another aspect of the present invention, the first lens unit moves from the enlargement side to the reduction side upon zooming from the wide-angle end to the telephoto end. In this case, the second lens group moves from the reduction side to the enlargement side upon zooming from the wide-angle end to the telephoto end. With this configuration, the zoom lens unit is used for focusing, the reduction lens unit is a fixed unit, and the intermediate lens unit is moved. It is possible to reduce the size.

  According to still another aspect of the present invention, the first lens unit is substantially fixed, the second lens unit is moved from the reduction side to the enlargement side, and the third lens unit is moved during zooming from the wide-angle end to the telephoto end. Move from the enlargement side to the reduction side. Also in this case, it is possible to reduce the size as compared with the above-described general four or more zoom lenses.

  According to still another aspect of the present invention, the zoom lens is a varifocal type, and the second lens unit moves from the reduction side to the enlargement side upon zooming from the wide-angle end to the telephoto end. By moving any one of the lens group and the third lens group, it is possible to correct both the focus movement by zoom and the focus focus movement when the projection distance is changed.

According to still another aspect of the present invention, the first lens group is configured by three lenses of two negative lenses and a positive lens in order from the magnification side, and the focal length of the first lens group is f1. The following conditional expression (2) is satisfied.
(2) 1.5 <| f1 / fw | <3.0
Conditional expression (2) relates to the power of the first lens group, and is intended to make it possible to obtain a sufficient back focus and suppress the occurrence of various aberrations. By exceeding the lower limit of the conditional expression (2), it is possible to avoid that the negative power of the first lens group becomes too strong, that is, the power of the two negative lenses becomes too strong. It is easy to correct the lateral chromatic aberration. Further, by falling below the upper limit of conditional expression (2), it can be avoided that the negative power of the first lens group becomes too weak, so that the power of the positive lens can be avoided from becoming too strong, and coma aberration and distortion aberration can be avoided. Can be easily corrected in a balanced manner.

According to still another aspect of the present invention, the second lens group includes, in order from the magnification side, a positive lens having a convex surface on the magnification side, a negative lens having a concave surface on the magnification side, and a concave surface on the magnification side. When the focal length of the second lens unit is f2, the negative lens and the positive lens with the convex surface facing the reduction side and the positive lens with the convex surface facing the enlargement side, and f2 Conditional expression (3) is satisfied.
(3) 1.5 <f2 / fw <3.5
Conditional expression (3) is a condition regarding the power of the second lens group. By exceeding the lower limit of conditional expression (3), the positive power of the second lens group does not become too strong, and it is possible to avoid the deterioration of spherical aberration and off-axis coma, and the coma flare increases throughout the screen. And a decrease in contrast can be avoided. That is, it becomes easy to obtain a bright F number, and it becomes easy to secure a sufficient amount of peripheral light. Also, by falling below the upper limit of conditional expression (3), the positive power of the second lens group does not become too weak, and it is possible to avoid an increase in the amount of movement of the second lens group at the time of zooming, which is called miniaturization. This is preferable. Further, since it is possible to avoid an increase in the amount of movement of the aperture stop position in the second lens group, it is possible to prevent the F number at the telephoto end from increasing and causing a temperature increase due to vignetting at the stop.

  According to still another aspect of the present invention, in the second lens group, the negative lens with the concave surface facing the enlargement side and the positive lens with the convex surface facing the reduction side are cemented lenses.

According to still another aspect of the present invention, the second lens group includes, in order from the magnification side, a positive lens having a convex surface on the magnification side, a negative lens having a concave surface on the magnification side, and a convex surface on the reduction side. When the focal length of the second lens unit is f2, the following conditional expression (3) is satisfied.
(3) 1.5 <f2 / fw <3.5

According to still another aspect of the present invention, when the radius of curvature of the most enlargement side surface of the second lens group is R1 and the radius of curvature of the most reduction side surface is R2, the following conditional expression (4) is satisfied. Satisfied.
(4) 0.5 <| R1 / R2 | <2.0
Conditional expression (4) is a condition regarding the radius of curvature of the second lens group. The second lens group has the largest amount of movement during zooming, and has a strong positive power because it mainly has a role of zooming. In addition, the second lens group efficiently captures the light beam diverged from the first lens group, and in order to obtain good telecentric characteristics in the subsequent third lens group, the most enlargement side surface and the most reduction side surface are It must have a relatively strong surface. For this reason, it is possible to correct various aberrations in a well-balanced manner by setting the radii of curvature on the most enlarged surface and the most reduced surface within the range of the conditional expression (4). By exceeding the lower limit of Conditional Expression (4), the radius of curvature of the most magnified surface of the second lens group is not too small compared to the most demagnifying surface, and spherical aberration and coma aberration can be kept small. This makes it possible to avoid difficulty and to obtain sufficient contrast. Conversely, by not exceeding the upper limit of conditional expression (4), the radius of curvature of the most magnified surface of the second lens group does not become too large compared to the most demagnifying surface, and astigmatism during zooming Aberrations can be corrected in a well-balanced manner, and the flatness of the image surface can be kept good.

According to still another aspect of the present invention, the first lens group includes at least one aspherical surface formed of a resin having negative power, and when the focal length of the resin aspherical lens is fp, Conditional expression (5) is satisfied.
(5) 2.5 <| fp / fw | <6.0
Resin lenses are easily affected by environmental changes such as temperature. By limiting the focal length of the resin lens, in other words, the power within the range of conditional expression (5), the influence of environmental changes is minimized. It is possible to obtain good performance.

  In order to achieve the above object, a projection image display apparatus according to the present invention is equipped with the projection zoom lens described above.

  Since the projection type image display apparatus is equipped with the projection zoom lens described above, it is possible to project a high-quality image with a projection zoom lens that is bright, has a relatively large angle of view, is compact, and is low in cost.

It is a figure which shows schematic structure of the projector incorporating the zoom lens for projection of embodiment. 1 is a diagram illustrating a configuration of a projection zoom lens according to an embodiment or Example 1. FIG. FIG. 6 is a diagram for explaining zooming of the optical system according to the first exemplary embodiment. FIG. 6 is a reduction aberration diagram of the projection zoom lens of Example 1; 6 is a diagram illustrating a configuration of a projection zoom lens according to Example 2. FIG. FIG. 10 is a diagram for explaining zooming of the optical system according to the second embodiment. 6 is a reduction side aberration diagram of the projection zoom lens of Example 2. FIG. 7 is a diagram illustrating a configuration of a projection zoom lens according to Example 3. FIG. FIG. 10 is a diagram for explaining zooming of an optical system according to a third embodiment. FIG. 10 is a reduction aberration diagram of the projection zoom lens according to Example 3; 6 is a diagram illustrating a configuration of a projection zoom lens according to Example 4. FIG. FIG. 10 is a diagram for explaining zooming of an optical system according to a fourth embodiment. FIG. 6 is a reduction side aberration diagram of the projection zoom lens of Example 4; FIG. 10 is a diagram illustrating a configuration of a projection zoom lens according to Example 5. FIG. 10 is a diagram for explaining zooming of an optical system according to a fifth embodiment. FIG. 10 is a reduction side aberration diagram of the projection zoom lens according to Example 5; FIG. 10 is a diagram illustrating a configuration of a projection zoom lens according to Example 6. FIG. 10 is a diagram for explaining zooming of an optical system according to a sixth embodiment. FIG. 11 is a reduction aberration diagram of the projection zoom lens according to Example 6;

  Hereinafter, a projection zoom lens according to an embodiment of the present invention and a projector (projection-type image display device) incorporating the same will be described with reference to the drawings.

  As shown in FIG. 1, a projector 100 that is a projection-type image display device incorporating a projection zoom lens according to an embodiment of the present invention includes an optical system portion 50 that projects image light, and the operation of the optical system portion 50. And a circuit device 80 for controlling the above.

  In the optical system portion 50, the light source 10 is an ultra-high pressure mercury lamp, for example, and emits light including R light, G light, and B light. Here, the light source 10 may be a discharge light source other than an ultra-high pressure mercury lamp, or may be a solid light source such as an LED or a laser. The first integrator lens 11 and the second integrator lens 12 have a plurality of lens elements arranged in an array. The first integrator lens 11 splits the light flux from the light source 10 into a plurality of parts. Each lens element of the first integrator lens 11 condenses the light beam from the light source 10 in the vicinity of the lens element of the second integrator lens 12. The lens elements of the second integrator lens 12 cooperate with the superimposing lens 14 to form images of the lens elements of the first integrator lens 11 on the liquid crystal panels 18R, 18G, and 18B. With such a configuration, the light from the light source 10 illuminates the entire display area of the liquid crystal panels 18R, 18G, and 18B with substantially uniform brightness.

  The polarization conversion element 13 converts light from the second integrator lens 12 into predetermined linearly polarized light. The superimposing lens 14 superimposes the image of each lens element of the first integrator lens 11 on the display area of the liquid crystal panels 18R, 18G, and 18B via the second integrator lens 12.

  The first dichroic mirror 15 reflects R light incident from the superimposing lens 14 and transmits G light and B light. The R light reflected by the first dichroic mirror 15 passes through the reflection mirror 16 and the field lens 17R and enters the liquid crystal panel 18R that is a light modulation element. The liquid crystal panel 18R forms an R color image by modulating the R light according to the image signal.

  The second dichroic mirror 21 reflects the G light from the first dichroic mirror 15 and transmits the B light. The G light reflected by the second dichroic mirror 21 passes through the field lens 17G and enters the liquid crystal panel 18G that is a light modulation element. The liquid crystal panel 18G modulates the G light according to the image signal to form a G color image. The B light transmitted through the second dichroic mirror 21 passes through the relay lenses 22 and 24, the reflection mirrors 23 and 25, and the field lens 17B and enters the liquid crystal panel 18B that is a light modulation element. The liquid crystal panel 18B forms a B-color image by modulating the B light according to the image signal.

  A cross prism (cross dichroic prism) 19 is a light combining prism, which combines light modulated by the liquid crystal panels 18R, 18G, and 18B into image light and advances it to the projection zoom lens 40.

  The projection zoom lens 40 is a projection optical system that enlarges and projects image light, which is modulated by the liquid crystal panels 18G, 18R, and 18B and synthesized by a cross prism (cross dichroic prism) 19, onto a screen (not shown).

  The circuit device 80 includes an image processing unit 81 to which an external image signal such as a video signal is input, and display driving for driving the liquid crystal panels 18G, 18R, and 18B provided in the optical system portion 50 based on the output of the image processing unit 81. Operation of the unit 82, a lens driving unit 83 that adjusts the state of the projection zoom lens 40 by operating a drive mechanism (not shown) provided in the projection zoom lens 40, and operations of these circuit portions 81, 82, 83, etc. And a main control unit 88 that controls the entire system.

  The image processing unit 81 converts the input external image signal into an image signal including a gradation of each color. The image processing unit 81 can also perform various image processing such as distortion correction and color correction on the external image signal.

  The display driving unit 82 can operate the liquid crystal panels 18G, 18R, and 18B based on the image signal output from the image processing unit 81, and can display an image corresponding to the image signal or an image that has been subjected to image processing. Corresponding images can be formed on the liquid crystal panels 18G, 18R, 18B.

  The lens driving unit 83 operates under the control of the main control unit 88 and performs projection by appropriately moving some optical elements constituting the projection zoom lens 40 along the optical axis OA via the actuator AC. In the projection of an image on the screen by the zoom lens 40, zooming and focusing (zoom and focus) can be performed. The lens driving unit 83 can also change the vertical position of the image projected on the screen by adjusting the tilt of moving the entire projection zoom lens 40 in the vertical direction perpendicular to the optical axis OA.

  Hereinafter, the projection zoom lens 40 of the embodiment will be described in detail with reference to FIG. Note that the projection zoom lens 40 illustrated in FIG. 2 and the like has the same configuration as the projection zoom lens 41 of Example 1 described later. For convenience, the + Y direction is the upward direction and the -Y direction is the downward direction.

  The projection zoom lens 40 according to the embodiment projects an image formed on the liquid crystal panel 18G (18R, 18B) onto a screen (not shown). Here, a prism PR corresponding to the cross dichroic prism 19 of FIG. 1 is disposed between the projection zoom lens 40 and the liquid crystal panel 18G (18R, 18B).

  The projection zoom lens 40 includes, in order from the magnification side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The three lens groups.

  The first lens group G1 includes three lens groups (lenses L11 to L13). Specifically, the first lens group G1 is composed of three lenses of two negative lenses (lenses L11 and L12) and one positive lens (lens L13) in order from the enlargement side. .

  The second lens group G2 is composed of a four-lens or five-lens group, and in the illustrated example, is composed of a five-lens group of lenses (lenses L21 to L25). Specifically, the second lens group G2 includes an aperture stop ST, and in order from the enlargement side, a single positive lens (lens L21) on the enlargement side, that is, the projection surface side with the convex surface facing the aperture stop ST. ), A negative lens (lens L22) having a concave surface facing the enlargement side, a negative lens (lens L23) having a concave surface facing the magnification side, and a cemented lens C21 having a positive lens (lens L24) having a convex surface facing the reduction side And a positive lens (lens L25) with a convex surface facing the enlargement side.

  The third lens group G3 is composed of one positive lens (lens L31) having a convex surface directed toward the enlargement side.

  In the zoom lens for projection 40 having the above-described configuration, the distance between the first lens group G1 and the second lens group G2 and the distance between the second lens group G2 and the third lens group G3 change during zooming and focusing. This zoom lens performs zooming and focusing. Among these, in the second lens group G2, the lens L21 arranged on the most enlargement side is a positive lens having a stronger convex surface on the enlargement side than the reduction side, and the lens L25 arranged on the most reduction side is the reduction side. This is a positive lens with a stronger convex surface than the magnification side.

In addition, the projection zoom lens 40 satisfies the following conditional expression (1).
(1) 1.4 <Bf / fw <2.0
However,
fw: focal length of the entire lens system at the wide angle end Bf: air-converted length of back focus excluding prisms and other flat plates The conditional expression (1) relates to the back focus. That is, the conditional expression (1) is a cross prism 19 (prism PR) arranged on the reduction side of the projection zoom lens 40 that is essential in the three-plate liquid crystal projector as in the projector 100 of this embodiment (see FIG. 1). ), A polarizing plate, other optical members, and the like, and by maintaining an appropriate interval, a space for smoothly cooling is ensured. By exceeding the lower limit of the conditional expression (1), it is possible to avoid the back focus from becoming too short, to secure a sufficient space for arranging an optical member such as the cross prism 19 (prism PR) on the reduction side, cooling, etc. It becomes easy. Also, by falling below the upper limit of conditional expression (1), it is possible to avoid an excessively long back focus while securing a space. When a substantially telecentric configuration is adopted on the reduction side, the lens diameter on the reduction side is large. You can avoid becoming too much.

Further, as described above, in the first lens group G1 constituted by two negative lenses (lenses L11 and L12) and one positive lens (lens L13), the focal length of the first lens group G1 is set. When f1, the following conditional expression (2) is satisfied.
(2) 1.5 <| f1 / fw | <3.0

  The first lens group G1 is composed of three lenses, which are two negative lenses (lenses L11 and L12) and one positive lens (lens L13), so that excellent distortion aberration can be achieved even in a wide angle of view. And chromatic aberration of magnification, and a relatively strong negative power in order to ensure a long back focus. Further, the first lens group G1 has an aspheric lens for the above aberration correction and the like. However, since the first lens group G1 has a relatively large diameter, the aspheric lens is a resin lens. It is preferable to do. However, resin lenses often cause focus movement due to changes in shape and refractive index due to environmental changes such as temperature and humidity. Therefore, it is preferable to reduce the power of the resin lens. Conditional expression (2) relates to the power of the first lens group G1, and is for making it possible to obtain a sufficient back focus and to suppress the occurrence of various aberrations. By exceeding the lower limit of conditional expression (2), it can be avoided that the negative power of the first lens group G1 becomes too strong, that is, the power of the two negative lenses (lenses L11 and L12) becomes too strong. Correction of magnification chromatic aberration and the like becomes easy. More specifically, when one of the two negative lenses (lenses L11 and L12) of the first lens group G1 is a resin lens as described above, the overall negative power is mainly used for the other non-resin. Although it is covered with a lens, if the lower limit of conditional expression (2) is exceeded, the lateral chromatic aberration occurring in the first lens group G1 can be corrected with the remaining one positive lens (lens L13). It becomes relatively easy. Further, by falling below the upper limit of conditional expression (2), it is possible to avoid the negative power of the first lens group G1 from becoming too weak, so it is possible to avoid the power of the positive lens from becoming too strong, and to reduce coma aberration and distortion. It becomes easy to correct aberrations in a balanced manner.

Further, the second lens group G2, in order from the magnification side, has a positive lens (lens L21) having a convex surface on the magnification side, a negative lens (lens L22) having a concave surface on the magnification side, and a concave surface on the magnification side. The lens is composed of five lenses: a negative lens (lens L23), a cemented lens C21 of a positive lens (lens L24) with a convex surface facing the reduction side, and a positive lens (lens L25) with a convex surface facing the magnification side. . Further, when the focal length of the second lens group G2 is f2, the following conditional expression (3) is satisfied.
(3) 1.5 <f2 / fw <3.5

  Conditional expression (3) is a condition regarding the power of the second lens group G2. The second lens group G2 is mainly involved in zooming and has a strong positive power. At the time of zooming from the wide-angle end to the telephoto end, the magnification of the image can be changed by moving the second lens group G2 from the reduction side to the enlargement side. At that time, since focus movement occurs, by moving the first lens group G1 or the third lens group G3, it is possible to correct the focus movement at the time of zooming and to function as a zoom lens. By exceeding the lower limit of conditional expression (3), the positive power of the second lens group G2 does not become too strong, and it is possible to avoid the deterioration of spherical aberration and off-axis coma, and the coma flare increases throughout the screen. And a decrease in contrast can be avoided. That is, it becomes easy to obtain a bright F number, and it becomes easy to secure a sufficient amount of peripheral light. Also, by falling below the upper limit of conditional expression (3), the positive power of the second lens group G2 does not become too weak, and the movement amount of the second lens group G2 at the time of zooming can be prevented from increasing. This is preferable from the viewpoint of conversion. Further, since it is possible to avoid an increase in the amount of movement of the position of the aperture stop ST in the second lens group G2, the F number at the telephoto end increases, which causes a temperature increase due to vignetting at the aperture stop ST. Can be prevented.

In the projection zoom lens 40, the radius of curvature of the most magnified surface (the lens surface on the enlargement side of the lens L21) of the second lens group G2 is R1, and the most reduction surface (the lens on the reduction side of the lens L25). When the radius of curvature of the surface is R2, the following conditional expression (4) is satisfied.
(4) 0.5 <| R1 / R2 | <2.0
The second lens group G2 has the largest amount of movement during zooming, and has a strong positive power because it mainly has a role of zooming. In addition, the second lens group G2 takes in the light beam diverged in the first lens group G1 efficiently, and obtains good telecentric characteristics in the subsequent third lens group G3, so that the most enlargement side and most reduction side are obtained. The surface must have a relatively strong surface. For this reason, it is possible to correct various aberrations in a well-balanced manner by setting the radii of curvature on the most enlarged surface and the most reduced surface within the range of the conditional expression (4). By exceeding the lower limit of Conditional Expression (4), the radius of curvature of the most magnified surface of the second lens group is not too small compared to the most demagnifying surface, and spherical aberration and coma aberration can be kept small. This makes it possible to avoid difficulty and to obtain sufficient contrast. Conversely, by not exceeding the upper limit of conditional expression (4), the radius of curvature of the most magnified surface of the second lens group does not become too large compared to the most demagnifying surface, and astigmatism during zooming Aberrations can be corrected in a well-balanced manner, and the flatness of the image surface can be kept good.

Further, as described above, an aspheric lens is generally used for the first lens group G1 in order to efficiently correct distortion and coma. The lens L12 of the first lens group G1 is composed of an aspheric lens formed of resin, and satisfies the following conditional expression (5) when the focal length of the aspheric lens is fp.
(5) 2.5 <| fp / fw | <6.0
Using a resin lens is easily affected by environmental changes such as temperature.For example, after focusing immediately after the projector is turned on, the focus position changes due to temperature changes in the installation environment or heat generation inside the projector over time. Is likely to move.
Conditional expression (5) relates to the power of the resin aspheric lens. By limiting the focal length of the resin lens, in other words, the power within the range of conditional expression (5), the influence of environmental changes is minimized. However, sufficient performance can be obtained.
By exceeding the lower limit of conditional expression (5), the focal length of the resin aspherical lens will not be too short, that is, the negative power will not be too strong. It is possible to make it difficult for focus movement to occur. Further, by not exceeding the upper limit of the conditional expression (5), the first lens group G1 is configured such that the focal length of the resin aspheric lens does not become too long, that is, the negative power does not become too weak. It is possible to avoid overloading one negative lens, and to balance a good image performance while maintaining a sufficient back focus.

  As described above, in the projection zoom lens 40 according to the present embodiment and the projector 100 which is a projection type image display apparatus incorporating the same, the first to third lens groups G1 to G3 constituting the projection zoom lens 40 are For example, the zoom lens can be configured as a zoom lens that moves the first and second lens groups G1 and G2 during zooming and moves the first lens group G1 during focusing. Furthermore, by exceeding the lower limit of conditional expression (1), the back focus does not become too short, and a sufficient space can be secured on the reduction side. Also, by falling below the upper limit of conditional expression (1), the back focus does not become too long while securing a space, and the lens diameter on the reduction side does not become too large when a substantially telecentric configuration is adopted on the reduction side. You can

〔Example〕
Examples of the projection zoom lens 40 will be described below. The meanings of specifications common to Examples 1 to 6 described below are summarized below.
f Focal length of the entire system FNo F number ω Half angle of view R Curvature radius D Top surface spacing (lens thickness or lens spacing)
Refractive index of Nd d line Vd Abbe number of d line

ただし、
ｃ： 曲率（１／Ｒ）
ｈ： 光軸からの高さ
ｋ： 非球面の円錐係数
Ａｉ：非球面の高次非球面係数
なお、面番号０は、スクリーン上の像面（被投射面）を意味し、ＳＴＯは開口絞りＳＴを意味し、面番号の最終番号は、パネル面ＰＩを意味する。また、面番号の前に「＊」が記載されている面は、非球面形状を有する面である。
（実施例１） The aspherical surface is specified by the following polynomial (aspherical surface equation).

However,
c: Curvature (1 / R)
h: Height from the optical axis k: Aspherical conical coefficient Ai: Aspherical higher-order aspherical coefficient Surface number 0 means the image surface (projected surface) on the screen, and STO is the aperture stop ST means the final number of the surface number means the panel surface PI. In addition, a surface having “*” written before the surface number is a surface having an aspherical shape.
Example 1

The lens surface data of Example 1 is shown in Table 1 below.
[Table 1]
Surface number RD Nd Vd
0 1800.000
1 69.448 1.800 1.74320 49.34
2 20.351 2.000
* 3 25.000 2.200 1.53116 56.04
* 4 14.793 11.499
5 36.861 3.000 1.75520 27.51
6 83.782 Variable interval
7 21.576 4.600 1.69700 48.52
8 1225.821 8.025
STO9 Infinity 3.600
* 10 -29.533 1.300 1.83441 37.28
* 11 864.058 2.281
12 -16.990 1.000 1.74000 28.30
13 40.805 6.200 1.59522 67.73
14 -19.406 0.200
15 139.432 7.000 1.62041 60.29
16 -23.349 Variable interval
17 46.927 3.600 1.56384 60.67
18 -375.789 6.000
19 Infinity 25.750 1.51680 64.20
20 Infinity 3.350
21 Infinity
Here, FIG. 2 shown as an embodiment of the projection zoom lens corresponds to a cross-sectional view of the projection zoom lens 40 (projection zoom lens 41) of the first embodiment.

Table 2 below shows the projection zoom lens 40 (projection zoom lens 41) including the case where the zoom lens is changed to the wide angle end (Wide), the intermediate focal length position (Middle), and the telephoto end (Tele) in the first embodiment. The ranges of the focal length f, the half angle of view ω, and the F number FNo of the entire system are shown. Further, the value of the axial upper surface distance D of the variable distance portion of the lens surfaces of Example 1 at the wide angle end, the intermediate focal length position, and the telephoto end is shown.
[Table 2]
f 16.9-20.28
FNo 1.60 ~ 1.75
ω 30.14 ° ~ 27.21 °
Surface number Wide Middle Tele
6 16.611 10.701 5.775
16 1.000 3.725 6.450

Table 3 below shows the aspheric coefficients of the lens surfaces of Example 1.
[Table 3]
Surface number K A04 A06 A08 A10 A12
3 0.0000 -2.2813E-05 0.0000E + 00 0.0000E + 00 0.0000E + 00 0.0000E + 00
4 -0.1570 -5.6884E-05 -1.5082E-07 4.6246E-10 -2.6102E-12 0.0000E + 00
10 -7.4112 4.0260E-05 -1.1765E-06 5.8088E-09 0.0000E + 00 0.0000E + 00
11 0.0000 1.3009E-04 -1.0703E-06 5.1539E-09 0.0000E + 00 0.0000E + 00
In Table 3 and the following table, a power of 10 (for example, 1.00 × 10 ⁺¹⁸ ) is expressed using E (for example, 1.00E + 18).

  The projection zoom lens 41 (corresponding to the projection zoom lens 40) of the first embodiment shown in FIGS. 2 and 3 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. In particular, FIG. 3 shows the state of the lens position at the wide-angle end in the upper stage, the state of the lens position at the intermediate focal length position in the middle stage, and the state of the lens position at the telephoto end in the lower stage. That is, the upper row shows the lens arrangement of the projection zoom lens 41 (projection zoom lens 41W) at the wide-angle end, and the middle row shows the lens of the projection zoom lens 41 (projection zoom lens 41M) at the intermediate focal length position. The lower part shows the lens arrangement of the projection zoom lens 41 (projection zoom lens 41T) at the telephoto end. Therefore, FIG. 3 shows the overall movement of the projection zoom lens 41 during zooming from the wide-angle end to the telephoto end.

  The projection zoom lens 41 includes, in order from the enlargement side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The three lens groups. As shown in FIG. 3, the third lens group G3 is fixed during zooming and focusing. On the other hand, during zooming from the wide-angle end to the telephoto end, the first lens group G1 moves from the enlargement side to the reduction side, and the second lens group G2 moves from the reduction side to the enlargement side. With such a configuration, for example, an enlargement-side lens group that can be considered as a general zoom lens having four or more groups is used for focusing, a reduction-side lens group is a fixed group, and an intermediate lens group (lens group) The zoom lens can be made smaller than a zoom lens having four or more groups of the type in which G2) is moved.

  Hereinafter, returning to FIG. 2, the details of each lens constituting the projection zoom lens 41 will be described.

  The first lens group G1 includes a first lens (lens L11) that is a negative meniscus lens having a convex surface facing the magnification side, and a second lens (lens L12) that is a negative meniscus lens having a convex surface facing the magnification side. And a third lens (lens L13) which is a positive meniscus lens having a convex surface facing the enlargement side. Among these, the second lens (lens L12) is a resin molded lens having aspheric surfaces on both sides.

  The second lens group G2 includes a fourth lens (lens L21) that is a positive meniscus lens that is disposed closest to the magnifying side and has a convex surface facing the magnifying side, and a biconcave negative fifth lens (lens L22). A cemented lens C21 of a biconcave negative sixth lens (lens L23) and a biconvex positive seventh lens (lens L24), and both arranged with the convex surface stronger than the magnifying side on the reduction side. Consists of five lenses including a convex positive eighth lens (lens L25). Among these, the fifth lens (lens L22) is a glass molded lens having aspheric surfaces on both sides. The aperture stop ST is provided between the fourth lens (lens L21) and the fifth lens (lens L22).

  The third lens group G3 is composed of a single positive lens (lens L31) having a convex surface directed toward the enlargement side.

  In other words, the projection zoom lens 41 is composed of nine lenses. The nine lenses L11 to L13, L21 to L25, and L31 have a circular shape that is symmetric about the optical axis OA. Of these, both surfaces of the second lens L12 and the fifth lens L22 are aspherical. All other surfaces are spherical.

  In the above case, the first lens group G1 and the second lens group G2 are moved by an interlocking mechanism such as a cam (not shown) at the time of zooming, and the first lens group G1 or the third lens is independent of this operation. When the group G3 is a focus group, it functions as a general zoom lens. Further, at the time of zooming, only the second lens group G2 is moved, and focus correction (focus movement accompanying zooming) is performed by the first lens group G1 or the third lens group G3, so that correction can be performed. Zoom (varifocal type) may be used.

  FIG. 4 is a diagram showing aberrations on the reduction side of the projection zoom lens. As shown in the figure, the upper stage shows the aberration at the wide-angle end, the middle stage at the intermediate focal length position, and the lower stage at the telephoto end. Further, in each stage, spherical aberration, astigmatism, and distortion are respectively shown in order from the left side. Here, aberrations at a reference wavelength of 550 nm and other wavelengths of 620 nm and 460 nm are shown.

(Example 2)
The lens surface data of Example 2 is shown in Table 4 below.
[Table 4]
Surface number RD Nd Vd
0 1800.000
* 1 22.577 2.200 1.53116 56.04
* 2 14.075 10.000
3 -188.832 1.500 1.66998 39.27
4 24.297 9.635
5 40.873 3.000 1.76182 26.52
6 139.605 Variable interval
7 25.064 4.200 1.78590 44.20
8 327.769 10.000
STO9 Infinity 5.284
* 10 -11.402 1.200 1.83441 37.28
* 11 -18.611 1.649
12 -19.682 1.300 1.74000 28.30
13 62.256 5.200 1.59522 67.73
14 -21.779 0.200
15 146.817 7.000 1.49700 81.54
16 -19.569 Variable interval
17 35.463 4.800 1.62041 60.29
18 984.815 6.000
19 Infinity 25.750 1.51680 64.20
20 Infinity 3.350
21 Infinity 0.000
Here, FIG. 5 is a sectional view of the projection zoom lens 40 (projection zoom lens 42) of the second embodiment.

Table 5 below shows the projection zoom lens 40 (projection zoom lens 42) including the case where the zoom lens is changed to the wide angle end (Wide), the intermediate focal length position (Middle), and the telephoto end (Tele) in the second embodiment. The ranges of the focal length f, the half angle of view ω, and the F number FNo of the entire system are shown. Moreover, the value of the axial upper surface distance D of the variable distance portion among the lens surfaces of Example 2 at each of the wide angle end, the intermediate focal length position, and the telephoto end is shown.
[Table 5]
f 16.9-20.28
FNo 1.60〜1.70
ω 30.01 ° ～ 25.86 °
Surface number Wide Middle Tele
6 9.527 5.020 1.263
16 1.000 5.097 9.194

Table 6 below shows the aspheric coefficients of the lens surfaces of Example 2.
[Table 6]
Surface number K A04 A06 A08 A10 A12
1 0.0000 -1.4265E-05 2.0886E-08 -6.0231E-11 0.0000E + 00 0.0000E + 00
2 -0.4340 -1.7137E-05 -1.8297E-08 5.2501E-11 -7.2535E-13 0.0000E + 00
10 -4.9583 2.1730E-04 -2.8668E-06 1.3734E-08 -3.7180E-11 2.2430E-13
11 -11.3316 3.4203E-04 -2.8960E-06 1.1572E-08 0.0000E + 00 0.0000E + 00

  The projection zoom lens 42 (corresponding to the projection zoom lens 40) of the second embodiment shown in FIGS. 5 and 6 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. In particular, FIG. 6 shows the projection zoom lens 42 at the wide-angle end (projection zoom lens 42W) at the upper stage and the projection zoom lens 42 (projection zoom lens 42 at the intermediate focal length position at the middle stage, as in the case shown in FIG. The lens arrangement of the projection zoom lens 42M) and the telephoto end projection zoom lens 42 (projection zoom lens 42T) are respectively shown in the lower stage. As a whole, the projection zoom at the time of zooming from the wide angle end to the telephoto end is shown. The state of movement of the lens 42 is shown.

  The projection zoom lens 42 includes, in order from the magnification side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The three lens groups. As shown in FIG. 6, the third lens group G3 is fixed during zooming and focusing. On the other hand, during zooming from the wide-angle end to the telephoto end, the first lens group G1 and the second lens group G2 move. Specifically, first, the first lens group G1 moves to the reduction side from the wide angle end to the intermediate focal length, but moves to the enlargement side from the intermediate focal length to the telephoto end. On the other hand, the second lens group G2 moves to the enlargement side during zooming from the wide-angle end to the telephoto end. As described above, when zooming from the corner end to the telephoto end, the first lens group G1 is moved from the enlargement side to the reduction side at the time of zooming from the wide angle end to the intermediate focal length position, and from the intermediate focal length position. When zooming from the telephoto end to the telephoto end, the zoom lens is moved to the enlargement side, that is, by moving the first lens group G1 to make a U-turn on the way, thereby zooming the first lens group G1 and the second lens. Even in the case where only the second group G2 is used, it is possible to reduce the focal position shift and facilitate zooming and focusing.

  Hereinafter, returning to FIG. 5, the details of each lens constituting the projection zoom lens 42 will be described.

  The first lens group G1 includes a first lens (lens L11) that is a negative meniscus lens having a convex surface facing the magnification side, a second lens (lens L12) that is a biconcave negative lens, and a convex surface on the magnification side. It is composed of three lenses including a third lens (lens L13) that is a positive meniscus lens. Among these, the first lens (lens L11) is a resin-molded lens having aspheric surfaces on both sides.

  The second lens group G2 is a fourth lens (lens L21) which is a positive meniscus lens disposed on the most enlargement side and having a convex surface facing the enlargement side, and a negative meniscus lens having a concave surface on the enlargement side. 5 lens (lens L22), a cemented lens C21 composed of a biconcave negative sixth lens (lens L23) and a biconvex positive seventh lens (lens L24), and arranged on the most reduction side and on the reduction side It is composed of five lenses including a biconvex positive eighth lens (lens L25) having a convex surface stronger than the magnification side. Among these, the fifth lens (lens L22) is a glass molded lens having aspheric surfaces on both sides. The aperture stop ST is provided between the fourth lens (lens L21) and the fifth lens (lens L22).

  The third lens group G3 is composed of a single positive lens (lens L31) having a convex surface directed toward the enlargement side.

  In other words, the projection zoom lens 42 is composed of nine lenses. The nine lenses L11 to L13, L21 to L25, and L31 have a circular shape that is symmetric about the optical axis OA. Of these, both surfaces of the first lens L11 and the fifth lens L22 are aspheric. All other surfaces are spherical.

  FIG. 7 is a diagram showing aberrations on the reduction side of the projection zoom lens. As shown in the figure, the upper stage shows the aberration at the wide-angle end, the middle stage at the intermediate focal length position, and the lower stage at the telephoto end. Further, in each stage, spherical aberration, astigmatism, and distortion are respectively shown in order from the left side.

(Example 3)
The lens surface data of Example 3 is shown in Table 7 below.
[Table 7]
Surface number RD Nd Vd
0 1800.000
1 42.958 1.800 1.74320 49.34
2 17.378 5.048
* 3 23.527 2.200 1.53116 56.04
* 4 13.929 13.020
5 41.582 3.000 1.67270 32.10
6 141.880 Variable interval
7 23.046 4.300 1.78590 44.20
8 84.433 10.000
STO9 Infinity 6.630
* 10 -10.117 1.200 1.83441 37.28
* 11 -14.658 0.829
12 -22.587 1.300 1.75520 27.51
13 63.856 0.100
14 69.186 4.400 1.59522 67.73
15 -29.359 0.200
16 325.331 7.000 1.49700 81.54
17 -16.969 Variable interval
18 31.996 4.200 1.62041 60.29
19 312.595 Variable interval
20 Infinity 25.750 1.51680 64.20
21 Infinity 3.350
22 Infinity
Here, FIG. 8 is a sectional view of the projection zoom lens 40 (projection zoom lens 43) of the third embodiment.

Table 8 below shows the projection zoom lens 40 (projection zoom lens 43) including the case where the zoom lens is changed to the wide angle end (Wide), the intermediate focal length position (Middle), and the telephoto end (Tele) in the third embodiment. The ranges of the focal length f, the half angle of view ω, and the F number FNo of the entire system are shown. In addition, the values of the axial upper surface distance D of the variable distance portions of the lens surfaces of Example 3 at the wide-angle end, the intermediate focal length position, and the telephoto end are shown.
[Table 8]
f 16.9-20.28
FNo 1.60 ~ 1.74
ω 29.54 ° ~ 25.69 ° Surface number Wide Middle Tele
6 9.911 5.247 1.008
17 0.994 5.994 10.373
19 6.767 6.431 6.291

Table 9 below shows the aspheric coefficients of the lens surfaces of Example 3.
[Table 9]
Surface number K A04 A06 A08 A10 A12
3 0.0000 -1.5508E-05 0.0000E + 00 0.0000E + 00 0.0000E + 00 0.0000E + 00
4 -2.4016 4.2318E-05 -2.7338E-07 7.1387E-10 -1.4059E-12 0.0000E + 00
10 -3.7512 2.2219E-04 -1.5765E-06 -1.4739E-08 2.2127E-10 -8.2619E-13
11 -1.8239 5.0496E-04 -3.6815E-06 1.2161E-08 0.0000E + 00 0.0000E + 00

  The projection zoom lens 43 (corresponding to the projection zoom lens 40) of the third embodiment shown in FIGS. 8 and 9 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. In particular, FIG. 9 shows the projection zoom lens 43 at the wide-angle end (projection zoom lens 43W) at the upper stage and the projection zoom lens 43 at the intermediate focal length position at the middle stage, as in the case shown in FIG. (Projection zoom lens 43M) and the lens arrangement of the telephoto end projection zoom lens 43 (projection zoom lens 43T) are respectively shown in the lower stage, and as a whole, for projection during zooming from the wide-angle end to the telephoto end The state of movement of the zoom lens 43 is shown.

  The projection zoom lens 43 includes, in order from the magnification side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The three lens groups. As shown in FIG. 9, the first lens group G1 is fixed (or substantially substantially fixed) during zooming and focusing. On the other hand, during zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the enlargement side, and the third lens group G3 moves to the reduction side. In this case, it is possible to reduce the size of the zoom lens as compared with the general zoom lens having four or more groups.

  Hereinafter, returning to FIG. 8, the details of each lens constituting the projection zoom lens 43 will be described.

  The first lens group G1 includes a first lens (lens L11) that is a negative meniscus lens having a convex surface facing the magnification side, and a second lens (lens L12) that is a negative meniscus lens having a convex surface facing the magnification side. And a third lens (lens L13) which is a positive meniscus lens having a convex surface facing the enlargement side. Among these, the second lens (lens L12) is a resin molded lens having aspheric surfaces on both sides.

  The second lens group G2 is a fourth lens (lens L21) which is a positive meniscus lens disposed on the most enlargement side and having a convex surface facing the enlargement side, and a negative meniscus lens having a concave surface on the enlargement side. 5 lenses (lens L22), biconcave negative sixth lens (lens L23), biconvex positive seventh lens (lens L24), arranged closest to the reduction side and stronger on the reduction side than the enlargement side It is composed of five lenses including a biconvex positive eighth lens (lens L25) having a convex surface. Among these, the fifth lens (lens L22) is a glass molded lens having aspheric surfaces on both sides. The aperture stop ST is provided between the fourth lens (lens L21) and the fifth lens (lens L22).

  The third lens group G3 is composed of a single positive lens (lens L31) having a convex surface directed toward the enlargement side.

  That is, the projection zoom lens 43 is composed of nine lenses. The nine lenses L11 to L13, L21 to L25, and L31 have a circular shape that is symmetric about the optical axis OA. Of these, both surfaces of the second lens L12 and the fifth lens L22 are aspherical. All other surfaces are spherical.

  FIG. 10 is a diagram showing aberrations on the reduction side of the projection zoom lens. As shown in the figure, the upper stage shows the aberration at the wide-angle end, the middle stage at the intermediate focal length position, and the lower stage at the telephoto end. Further, in each stage, spherical aberration, astigmatism, and distortion are respectively shown in order from the left side.

Example 4
The lens surface data of Example 4 is shown in Table 10 below.
[Table 10]
Surface number RD Nd Vd
0 1800
* 1 39.246 2.200 1.53116 56.04
* 2 17.782 6.747
3 -63.838 1.500 1.80100 34.97
4 27.213 6.296
5 49.049 5.200 1.72825 28.46
6 -74.580 Variable spacing
7 23.537 4.600 1.63854 55.38
8 -1900.229 13.039
STO9 Infinity 2.800
* 10 -12.005 1.200 1.83220 40.10
* 11 -18.458 1.474
12 -14.900 1.300 1.76182 26.52
13 -135.656 4.800 1.59522 67.73
14 -15.820 0.200
15 208.758 7.200 1.49700 81.54
16 -19.130 Variable interval
17 53.418 3.800 1.62041 60.29
18 -2354.845 6.000
19 Infinity 25.750 1.51680 64.20
20 Infinity 3.350
21 Infinity
Here, FIG. 11 is a sectional view of the projection zoom lens 40 (projection zoom lens 44) of the fourth embodiment.

Table 11 below shows the projection zoom lens 40 (projection zoom lens 44) including the case where the zoom lens is changed to the wide angle end (Wide), the intermediate focal length value (Middle), and the telephoto end (Tele) in the fourth embodiment. The ranges of the focal length f, the half angle of view ω, and the F number FNo of the entire system are shown. In addition, the values of the axial upper surface distance D of the variable distance portions of the lens surfaces of Example 4 at the wide-angle end, the intermediate focal length position, and the telephoto end are shown.
[Table 11]
f 16.9-20.28
FNo 1.60〜1.72
ω 30.16 ° ~ 25.88 °
Surface number Wide Middle Tele
6 12.521 6.262 1.047
16 1.000 3.598 6.197

Table 12 below shows the aspheric coefficients of the lens surfaces of Example 4.
[Table 12]
Surface number K A04 A06 A08 A10 A12
1 0.0000 2.2692E-06 -3.1379E-08 7.1340E-11 0.0000E + 00 0.0000E + 00
2 -0.4943 -3.8315E-06 -7.8162E-08 -1.5588E-11 2.3954E-13 0.0000E + 00
10 -3.6972 2.1313E-04 -2.9179E-06 1.7048E-08 -1.3996E-10 8.0145E-13
11 -7.1228 3.1121E-04 -2.2787E-06 6.8914E-09 0.0000E + 00 0.0000E + 00

  The projection zoom lens 44 (corresponding to the projection zoom lens 40) of the fourth embodiment shown in FIGS. 11 and 12 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. In particular, FIG. 12 shows the projection zoom lens 44 at the wide-angle end (projection zoom lens 44W) at the upper stage, and the projection zoom lens 44 at the intermediate focal length position at the middle stage, as in the case shown in FIG. The lens arrangement of the projection zoom lens 44M (projection zoom lens 44T) and the telephoto end projection zoom lens 44 (projection zoom lens 44T) are respectively shown in the lower part, and as a whole, for projection during zooming from the wide-angle end to the telephoto end. The movement of the zoom lens 44 is shown.

  The projection zoom lens 44 includes, in order from the magnification side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The three lens groups. As shown in FIG. 12, the third lens group G3 is fixed during zooming and focusing. On the other hand, during zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the reduction side, and the second lens group G2 moves to the enlargement side.

  Hereinafter, returning to FIG. 11, the details of each lens constituting the projection zoom lens 44 will be described.

  The first lens group G1 includes a first lens (lens L11) that is a negative meniscus lens having a convex surface facing the enlargement side, a second lens (lens L12) that is a biconcave negative lens, and a biconvex positive lens. It consists of three lenses with a third lens (lens L13). Among these, the first lens (lens L11) is a resin-molded lens having aspheric surfaces on both sides.

  The second lens group G2 includes a biconvex positive fourth lens (lens L21) that is disposed closest to the magnifying side and has a convex surface that is stronger on the magnifying side than the reducing side, and a negative meniscus lens that has a concave surface on the magnifying side. A fifth lens (lens L22), a sixth lens (lens L23) that is a negative meniscus lens having a concave surface facing the enlargement side, and a seventh lens (lens) that is a positive meniscus lens having a concave surface facing the magnification side L24) and a cemented lens C21, and a biconvex positive eighth lens (lens L25) that is disposed closest to the reduction side and has a stronger convex surface on the reduction side than the enlargement side. Among these, the fifth lens (lens L22) is a glass molded lens having aspheric surfaces on both sides. The aperture stop ST is provided between the fourth lens (lens L21) and the fifth lens (lens L22).

  The third lens group G3 is composed of a single positive lens (lens L31) having a convex surface directed toward the enlargement side.

  That is, the projection zoom lens 44 is composed of nine lenses. The nine lenses L11 to L13, L21 to L25, and L31 have a circular shape that is symmetric about the optical axis OA. Of these, both surfaces of the first lens L11 and the fifth lens L22 are aspheric. All other surfaces are spherical.

  FIG. 13 is a diagram showing aberrations on the reduction side of the projection zoom lens. As shown in the drawing, the upper stage shows the aberration at the wide-angle end, the middle stage at the intermediate focal length position, and the lower stage at the telephoto end. Further, in each stage, spherical aberration, astigmatism, and distortion are respectively shown in order from the left side.

(Example 5)
The lens surface data of Example 5 is shown in Table 13 below.
[Table 13]
Surface number RD Nd Vd
0 1800.000
* 1 23.262 2.200 1.53116 56.04
* 2 14.569 9.773
3 1024.368 1.800 1.72916 54.68
4 24.630 11.149
5 37.661 2.600 1.72825 28.46
6 80.550 Variable interval
7 20.760 4.500 1.71700 47.93
8 650.554 10.000
STO9 Infinity 0.995
* 10 -25.366 1.200 1.83441 37.28
* 11 1824.594 2.556
12 -16.904 1.100 1.73800 32.26
13 36.723 6.200 1.61800 63.33
14 -18.257 0.200
15 88.397 7.300 1.49700 81.54
16 -21.338 Variable interval
17 34.964 4.800 1.48749 70.24
18 -955.076 Variable spacing
19 Infinity 25.750 1.51680 64.20
20 Infinity 3.350
21 Infinity
Here, FIG. 14 is a sectional view of the projection zoom lens 40 (projection zoom lens 45) of the fifth embodiment.

Table 14 below shows the projection zoom lens 40 (projection zoom lens 45) including the case where the zoom lens is changed to the wide angle end (Wide), the intermediate focal length position (Middle), and the telephoto end (Tele) in Example 5. The ranges of the focal length f, the half angle of view ω, and the F number FNo of the entire system are shown. In addition, the values of the axial upper surface distance D of the variable distance portions of the lens surfaces of Example 5 at the wide-angle end, the intermediate focal length position, and the telephoto end are shown.
[Table 14]
f 16.9-20.28
FNo 1.60〜1.76
ω 29.81 ° ~ 25.66 °
Surface number Wide Middle Tele
6 8.722 4.670 1.000
16 1.000 5.420 9.202
18 6.839 6.446 6.329

Table 15 below shows aspheric coefficients of the lens surfaces of Example 5.
[Table 15]
Surface number K A04 A06 A08 A10 A12
1 0.0000 -4.0696E-06 -1.8924E-08 0.0000E + 00 0.0000E + 00 0.0000E + 00
2 -0.3468 -5.8310E-06 -8.4055E-08 1.1463E-10 -7.2766E-13 0.0000E + 00
10 0.3030 1.4018E-04 -2.1465E-06 9.8215E-09 4.2235E-11 -3.0497E-13
11 0.0000 1.9665E-04 -1.9373E-06 1.0638E-08 0.0000E + 00 0.0000E + 00

  The projection zoom lens 45 (corresponding to the projection zoom lens 40) of Example 5 shown in FIGS. 14 and 15 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. In particular, FIG. 15 shows the projection zoom lens 45 at the wide-angle end (projection zoom lens 45W) at the upper stage and the projection zoom lens 45 at the intermediate focal length position at the middle stage as in the case shown in FIG. (Projection zoom lens 45M) and the lower lens arrangement of the telephoto end projection zoom lens 45 (projection zoom lens 45T) are shown respectively, and as a whole, for projection during zooming from the wide-angle end to the telephoto end The movement of the zoom lens 45 is shown.

  The projection zoom lens 45 includes, in order from the magnification side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The three lens groups. As shown in FIG. 15, the first lens group G1 is fixed (or substantially substantially fixed) during zooming and focusing. On the other hand, during zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the enlargement side, and the third lens group G3 moves to the reduction side. In this case, it is possible to reduce the size of the zoom lens as compared with the general zoom lens having four or more groups.

  Hereinafter, returning to FIG. 14, the details of each lens constituting the projection zoom lens 45 will be described.

  The first lens group G1 includes a first lens (lens L11) that is a negative meniscus lens having a convex surface facing the magnification side, and a second lens (lens L12) that is a negative meniscus lens having a convex surface facing the magnification side. And a third lens (lens L13) which is a positive meniscus lens having a convex surface facing the enlargement side. Among these, the first lens (lens L11) is a resin-molded lens having aspheric surfaces on both sides.

  The second lens group G2 includes a fourth lens (lens L21) that is a positive meniscus lens that is disposed closest to the magnifying side and has a convex surface facing the magnifying side, and a biconcave negative fifth lens (lens L22). A cemented lens C21 of a biconcave negative sixth lens (lens L23) and a biconvex positive seventh lens (lens L24), and a convex surface that is arranged closest to the reduction side and has a stronger convex surface than the enlargement side. It is composed of five lenses including a biconvex positive eighth lens (lens L25). Among these, the fifth lens (lens L22) is a glass molded lens having aspheric surfaces on both sides. The aperture stop ST is provided between the fourth lens (lens L21) and the fifth lens (lens L22).

  The third lens group G3 is composed of a single positive lens (lens L31) having a convex surface directed toward the enlargement side.

  In other words, the projection zoom lens 45 is composed of nine lenses. The nine lenses L11 to L13, L21 to L25, and L31 have a circular shape that is symmetric about the optical axis OA. Of these, both surfaces of the first lens L11 and the fifth lens L22 are aspheric. All other surfaces are spherical.

  FIG. 16 is a diagram showing aberrations on the reduction side of the projection zoom lens. As shown in the drawing, aberrations at the wide-angle end in the upper stage, the intermediate focal length position in the middle stage, and the telephoto end in the lower stage are shown. Further, in each stage, spherical aberration, astigmatism, and distortion are respectively shown in order from the left side.

(Example 6)
The lens surface data of Example 6 is shown in Table 16 below.
[Table 16]
Surface number RD Nd Vd
0 Infinity 1800.000
1 174.573 1.400 1.74320 49.34
2 19.615 2.562
* 3 36.052 2.200 1.53116 56.04
* 4 16.312 8.698
5 43.170 3.600 1.76200 40.10
6 -727.779 Variable spacing
7 29.299 4.200 1.74400 44.79
8 -2418.371 12.677
STO9 Infinity 6.500
* 10 -20.402 1.600 1.82115 24.06
* 11 109.296 3.296
12 -48.795 4.000 1.59522 67.73
13 -21.983 0.100
14 413.917 8.000 1.49700 81.54
15 -18.348 Variable interval
16 43.904 4.400 1.48749 70.24
17 -184.265 Variable interval
18 Infinity 25.750 1.51680 64.20
19 Infinity 3.350
20 Infinity
Here, FIG. 17 is a cross-sectional view of the projection zoom lens 40 (projection zoom lens 46) of the sixth embodiment.

Table 17 below shows the projection zoom lens 40 (projection zoom lens 46) including the case where the zoom lens is changed to the wide angle end (Wide), the intermediate focal length position (Middle), and the telephoto end (Tele) in Example 6. The ranges of the focal length f, the half angle of view ω, and the F number FNo of the entire system are shown. In addition, the values of the axial upper surface distance D of the variable distance portions of the lens surfaces of Example 6 at the wide angle end, the intermediate focal length position, and the telephoto end are shown.
[Table 17]
f 16.9-20.28
FNo 1.60〜1.71
ω 29.88 ° ~ 25.71 °
Surface number Wide Middle Tele
6 12.691 6.314 1.000
16 0.750 3.896 7.028
18 6.252 6.298 6.351

Table 18 below shows aspheric coefficients of the lens surfaces of Example 6.
[Table 18]
Surface number K A04 A06 A08 A10 A12
3 0.0000 -3.1515E-06 -4.9414E-08 1.3814E-10 0.0000E + 00 0.0000E + 00
4 -0.7501 -2.8248E-05 -1.1195E-07 4.1416E-10 -7.7085E-13 0.0000E + 00
10 -2.0000 -5.8045E-05 -8.8805E-08 -3.8033E-10 -1.2210E-12 0.0000E + 00
11 -1.0000 2.6899E-05 9.1087E-09 -1.1630E-10 -4.4205E-13 0.0000E + 00

  The projection zoom lens 46 (corresponding to the projection zoom lens 40) of Example 6 shown in FIGS. 17 and 18 enlarges and projects an image on the panel surface PI at a magnification according to the distance to the screen. In particular, FIG. 18 shows the projection zoom lens 46 at the wide-angle end (projection zoom lens 45W) at the upper stage and the projection zoom lens 46 at the intermediate focal length position at the middle stage, as in the case shown in FIG. (Projection zoom lens 46M) and the lens arrangement of the telephoto end projection zoom lens 46 (projection zoom lens 46T) are respectively shown in the lower stage, and as a whole, for projection during zooming from the wide-angle end to the telephoto end. The movement of the zoom lens 46 is shown.

  The projection zoom lens 46 includes, in order from the magnification side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. The three lens groups. As shown in FIG. 18, all of the first to third lens groups G1 to G3 move during zooming and focusing. Specifically, during zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the reduction side, the second lens group G2 moves to the enlargement side, and the third lens group G3 slightly enlarges. Move to the side.

  Hereinafter, returning to FIG. 17, the details of each lens constituting the projection zoom lens 46 will be described.

  The first lens group G1 includes a first lens (lens L11) that is a negative meniscus lens having a convex surface facing the magnification side, and a second lens (lens L12) that is a negative meniscus lens having a convex surface facing the magnification side. , And is composed of three lenses including a biconvex positive third lens (lens L13). Among these, the second lens (lens L12) is a resin molded lens having aspheric surfaces on both sides.

  The second lens group G2 includes a biconvex positive fourth lens (lens L21) disposed on the most magnifying side and having a convex surface on the magnifying side that is stronger than the reduction side, and a biconcave negative fifth lens (lens L22). ), A sixth lens (lens L23) that is a positive meniscus lens having a concave surface facing the enlargement side, and a biconvex positive seventh lens disposed on the most reduction side and having a stronger convex surface on the reduction side than the enlargement side The lens is composed of four lenses (lens L24). Among these, the fifth lens (lens L22) is a glass molded lens having aspheric surfaces on both sides. The aperture stop ST is provided between the fourth lens (lens L21) and the fifth lens (lens L22).

  The third lens group G3 is composed of one positive lens (lens L31) having a convex surface directed toward the enlargement side.

  That is, the projection zoom lens 46 is composed of eight lenses. The eight lenses L11 to L13, L21 to L24, and L31 have an axisymmetric circular shape with respect to the optical axis OA. Of these, both surfaces of the second lens L12 and the fifth lens L22 are aspherical. All other surfaces are spherical.

  FIG. 19 is a reduction aberration diagram of the projection zoom lens. As shown in the drawing, aberrations at the wide-angle end in the upper stage, the intermediate focal length position in the middle stage, and the telephoto end in the lower stage are shown. Further, in each stage, spherical aberration, astigmatism, and distortion are respectively shown in order from the left side.

(Summary of Examples)
Hereinafter, consideration regarding conditional expressions (1) to (4) for the above-described Examples 1 to 6 will be made.

Table 19 below shows numerical values in the respective examples regarding the conditional expressions (1) to (5). It turns out that all satisfy | fill the range (condition) of conditional expression (1)-(5).
[Table 19]
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
(1) 1.4 <Bf / fw <2 1.557 1.557 1.589 1.557 1.593 1.557
(2) 1.5 <| f1 / fw | <3 2.505 2.192 2.555 2.469 2.110 2.449
(3) 1.5 <f2 / fw <3.5 2.491 2.667 2.893 2.503 2.492 2.794
(4) 0.5 <| R1 / R2 | <2 0.924 1.281 1.358 1.230 0.973 1.597
(5) 2.5 <| fp / fw | <6 4.347 4.558 4.117 3.742 4.744 3.440

  As described above, in the projection zoom lens (projection optical system) of the present embodiment or the projection type image display apparatus (projector) using the same, the lens group constituting the projection system (projection system) has a three-group configuration. Yes, when zooming, for example, the first and second lens groups, or the second lens group alone, the second and third lens groups, or all of the first to third lens groups are moved. It can be configured as a zoom lens of a type that moves the lens group. Furthermore, by exceeding the lower limit of conditional expression (1), the back focus does not become too short, and a sufficient space can be secured on the reduction side. Also, by falling below the upper limit of conditional expression (1), the back focus does not become too long while securing a space, and the lens diameter on the reduction side does not become too large when a substantially telecentric configuration is adopted on the reduction side. You can

  The present invention is not limited to the above embodiments or examples, and can be implemented in various modes without departing from the scope of the invention.

  For example, in each embodiment, one or more lenses having substantially no power can be added before, after, or between the lenses constituting each lens group.

  Further, the object of enlargement projection by the projection zoom lens 40 which is a projection optical system is not limited to an image formed by a liquid crystal panel, and an image formed by a light modulation element such as a digital micromirror device is enlarged and projected. be able to.

  AC ... actuator, C21 ... cemented lens, G1 ... first lens group, G2 ... second lens group, G3 ... third lens group, L11-L13, L21-L25, L31 ... lens, OA ... optical axis, PI ... panel Surface, f ... focal length, ω ... half angle of view, PR ... prism, 11, 12 ... integrator lens, 13 ... polarization conversion element, 14 ... superimposed lens, 15 ... dichroic mirror, 16 ... reflection mirror, 17B, 17G, 17R ... Field lens, 18G, 18R, 18B ... Liquid crystal panel, 19 ... Cross prism (cross dichroic prism), 21 ... Dichroic mirror, 22 ... Relay lens, 23 ... Reflection mirror, 40-46 ... Projection zoom lens (projection optical system) ), 50 ... optical system part, 80 ... circuit device, 81 ... image processing part, 82 ... display drive part, 83 ... lens drive Moving part, 88 ... main control part, 100 ... projector (projection-type image display device)

Claims (12)

In order from the enlargement side, the first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power,
A zoom lens that performs zooming and focusing by changing a distance between the first lens group and the second lens group and a distance between the second lens group and the third lens group during zooming and focusing. ,
The second lens group is arranged on the most enlargement side and has a convex surface on the enlargement side, the reduction side is a convex lens or a concave surface that is weaker than the enlargement side, and is disposed on the most reduction side and has a convex surface on the reduction side, A positive lens having a concave surface on the enlargement side, or a convex surface on which the enlargement side is weaker than the reduction side,
The third lens group is composed of one positive lens having a convex surface on the enlargement side,
A zoom lens for projection that satisfies the following conditional expression (1).
(1) 1.4 <Bf / fw <2.0
However,
fw: focal length of the entire lens system at the wide angle end Bf: air equivalent length of back focus   During zooming from the wide-angle end to the telephoto end, the first lens group moves from the enlargement side to the reduction side during zooming from the wide-angle end to a predetermined intermediate focal length position, and from the intermediate focal length position. The zoom lens for projection according to claim 1, wherein the zoom lens moves from the reduction side to the enlargement side during zooming to the telephoto end.   The projection zoom lens according to claim 1, wherein the first lens group moves from the enlargement side to the reduction side upon zooming from the wide-angle end to the telephoto end.   Upon zooming from the wide-angle end to the telephoto end, the first lens group is substantially fixed, the second lens group moves from the reduction side to the enlargement side, and the third lens group moves from the enlargement side to the reduction side. The projection zoom lens according to claim 1.   During zooming from the wide-angle end to the telephoto end, the second lens group moves from the reduction side to the enlargement side, and the focal point movement associated with zooming is changed to one of the first lens group and the third lens group. The projection zoom lens according to claim 1, wherein the projection zoom lens can be corrected by being moved. The first lens group is composed of three lenses of two negative lenses and a positive lens in order from the magnification side,
The projection zoom lens according to claim 1, wherein the following conditional expression (2) is satisfied when a focal length of the first lens group is f1.
(2) 1.5 <| f1 / fw | <3.0 The second lens group includes, in order from the magnifying side, a positive lens having a convex surface on the magnifying side, a negative lens having a concave surface on the magnifying side, a negative lens having a concave surface on the magnifying side, and a convex surface on the reducing side When the focal length of the second lens group is f2, the following conditional expression (3) is satisfied. The projection zoom lens according to any one of claims 1 to 6.
(3) 1.5 <f2 / fw <3.5   8. The projection zoom lens according to claim 7, wherein in the second lens group, the negative lens having a concave surface facing the enlargement side and the positive lens having a convex surface facing the reduction side are cemented lenses. 9. The second lens group includes, in order from the magnification side, a positive lens having a convex surface on the magnification side, a negative lens having a concave surface on the magnification side, a positive lens having a convex surface on the reduction side, and a convex surface on the magnification side. 7. The optical system according to any one of claims 1 to 6, wherein the second lens group is configured by four lenses that are directed positive lenses, and satisfies the following conditional expression (3) when the focal length of the second lens group is f2. A zoom lens for projection according to the item.
(3) 1.5 <f2 / fw <3.5 The following conditional expression (4) is satisfied, where R1 is a radius of curvature of the most enlargement surface of the second lens group and R2 is a radius of curvature of the most reduction surface. Projection zoom lens.
(4) 0.5 <| R1 / R2 | <2.0 The first lens group includes an aspheric lens having negative power and formed of at least one resin. When the focal length of the aspheric lens is fp, the following conditional expression (5) is satisfied. The zoom lens for projection according to claim 1.
(5) 2.5 <| fp / fw | <6.0   A projection-type image display device equipped with the projection zoom lens according to claim 1.

Images